Six Weight-Loss Myths Busted

If you want to lose weight, don't sabotage your diet with these common misconceptions.

After weeks of holiday indulgences, many runners are ready to start the New Year on a healthier foot, and often that means shedding pounds. But even the most health-savvy runners can get caught up in diet myths that sabotage their goals. "Weight loss is so complex and confusing because there is so much conflicting information out there," says Leslie Bonci, M.P.H., R.D., director of sports nutrition at the University of Pittsburgh Medical Center. With our experts' help and the latest research, we've dispelled five myths so you can start slimming down for good.

Myth: NO SWEETS BEFORE NOONMost runners who want to lose weight assume they have to forgo dessert. But not only can you have it, you can have it for breakfast, according to a study published in March 2012 in the journal Steroids: Researchers found that participants who ate a 600-calorie, carb- and protein-rich breakfast that included dessert, such as chocolate or ice cream, lost more weight over four months (and kept more off the following four months) than a group that ate a low-carb morning meal. "Dessert for breakfast sounds so sinful," says Bonci, "but if you allow yourself a tad more indulgent breakfast, you might eat less during the day instead of trying to be really 'good' and overcompensating later."Make it work: Eat a 600-calorie or so breakfast rich in vegetables, fruit, protein, and carbs, and add a sweet if you crave it. Avoid calorie bombs, like mega chocolate chip muffins, says Bonci; instead, have a shake made with vanilla yogurt, banana, peanut butter, and a little chocolate, or a banana muffin with almond butter.

Myth: ADDED FIBER KEEPS YOU FULLHigh-fiber foods, like fruits and vegetables, take longer to digest and hold more water, which is why they fill you up and aid weight loss. Companies have capitalized on this by adding fiber to everything from yogurt to snack bars. But do these fibers work? University of Minnesota researchers had participants replace two meals a day with a low-fiber snack bar or one that contained 10 grams of added fiber. The results (published in the Journal of the Academy of Nutrition and Dietetics) show the added fiber had no effect on fullness and caused more bloating than the low-fiber bars. "Everyone in the food industry is jumping on the fiber bandwagon," says Bonci, "but as this study shows, not all fibers are created equal."Make it work: To quell hunger, Bonci recommends sticking with foods naturally high in fiber--whole grains, beans, fruits, and vegetables. They tend to be lower-calorie and take up more room in the stomach than processed foods with fiber.

Myth: CARBS LEAD TO WEIGHT GAINRunners know carbs are essential for training, but many still cut back if they're trying to lose weight. After all, eating lots of carbs, as you would prerace, causes the scale to go up. "Carbs act like a sponge," says Bonci, "helping you absorb water." That weight is temporary and means you're well fueled. But there's more reason to keep carbs--whole-grain carbs--in your diet. According to a study published in April 2012, participants who ate a low-calorie diet high in whole wheat for 12 weeks lost more fat than a group that ate a low-cal diet high in refined wheat, most likely because the extra fiber in whole grains was more filling.Make it work: Whenever you eat grains, make them whole, says Katherine Beals, Ph.D., R.D., an associate professor at the University of Utah. To make this a reality, cook a large batch of grains to eat all week. Add different nuts, dried fruits, vegetables, and meats to vary the flavors.

Myth: CUT ALL FATFat is the most calorie-dense nutrient, so it would make sense that eating less of it would help you lose weight. But slashing your fat intake may have the opposite effect. In a study published in the Journal of the American Medical Association, researchers compared participants on three diets--low-fat, low-glycemic, and low-carb. Eating a low-fat diet decreased resting energy expenditure (or the number of calories you burn at rest) the most. Cutting back on fat also affected hormones essential to keeping cholesterol and insulin in check. "We need fat for many reasons," says Bonci. "It's an important fuel source for exercise. If you don't consume enough, your body will burn muscle."Make it work: "When people eat a low-fat diet, they add flavor other ways, like by eating sugar," says Bonci. She recommends 30 percent of your calories come from fat--and two-thirds of that should be the healthy unsaturated kinds from nuts, oils, fish, eggs, and avocados.

Myth: YOU SHOULD ONLY USE ZERO-CALORIE SWEETENERSFor runners looking to shed pounds, using zero-calorie sweeteners, such as sucralose, aspartame, and stevia, may be an appealing choice, since swapping out a sugar-packed soda for a diet version is an easy way to cut calories. But according to a joint study statement by the American Heart Association and the American Diabetes Association, the scientific evidence connecting zero-calorie sweeteners with long-term weight loss is inconclusive. Why? One of the main problems is overcompensation. If you save 150 calories by drinking a diet soda, but then reward yourself with an extra helping at dinner, you've negated any calorie-saving benefit.Make it work: "If you drink lots of soda or add tons of sugar to your coffee," says Bonci, "you may want to try diet versions." However, "if using a zero-calorie sweetener gives you license in your mind to eat whatever you want, then it's not the right choice for you. You have to make sure cutting back in one arena doesn't prompt you to overdo it in another."

Myth: ADD MORE LONG RUNSMany runners assume that going longer is always better--especially when it comes to weight loss. But a recent Danish study published in September 2012 found that this isn't always the case. During the study, researchers had overweight participants do 30 or 60 minutes of moderate exercise a day. Surprisingly, those who exercised less lost more weight during the 13-week study. What's the catch? The group that exercised longer ended up eating more throughout the day than the moderate-exercise group. In other words, the longer they exercised, the more they overcompensated for it.Make it work: Running long is good, but not if you overeat because of it, says Beals. Make sure you pay attention to your diet on days you do run long. On the flip side, beginners should be encouraged to know you don't need to run for hours to see real weight loss results.